This was sent by a friend and it tickled me so much I had to post it!
Anyone care to add to the list?

From the Washington Post Style Invitation, in which it was postulated that English should have male and female nouns, and readers were asked to assign a gender to nouns of their choice and explain their reason.

The best submissions:

SWISS ARMY KNIFE - male
Because even though it appears useful for a wide variety of work, it spends most of its time just opening bottles.

KIDNEYS - female
Because they always go to the bathroom in pairs.

PENLIGHT - male
Because it can be turned on very easily, but isn't very bright.

TIRE - male
Because it goes bald and often is over-inflated.

HOT AIR BALLOON - male
Because to get it to go anywhere you have to light a fire under it...
and, of course, there's the hot air part.

SPONGES - female
Because they are soft and squeezable and retain water.

WEB PAGE - female
Because it is always getting hit on.

SHOE - male
Because it is usually unpolished, with its tongue hanging out.

COPIER - female
Because once turned off, it takes a while to warm up.
Because it is an effective reproductive device when the right buttons are pushed.
Because it can wreak havoc when the wrong buttons are pushed.

ZIPLOC BAGS - male
Because they hold everything in, but you can always see right through them.

SUBWAY - male
Because it uses the same old lines to pick people up.

HOURGLASS - female
Because over time, the weight shifts to the bottom.

HAMMER - male
Because it hasn't evolved much over the last 5,000 years, but it's handy to have around and is good for killing bugs.